Novel Tunable Permanent Magnet Quadrupoles for the CLIC Drive Beam
Design of Nb 3 Sn IR quadrupoles with apertures larger than 120 mm
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Transcript of Design of Nb 3 Sn IR quadrupoles with apertures larger than 120 mm
Design of Nb3Sn IR quadrupoles with apertures larger than 120 mm
Paolo Ferracin and Ezio Todesco
1st HiLumi LHC / LARP Collaboration Meeting CERN
16-18 November, 2011
Introduction• Upgrade of the LHC IR quadrupoles
– From Nb-Ti 70 mm bore (MQXA from Japan, MQXB from US) to larger apertures
• Currently under development, 120 mm aperture quadrupoles– Nb-Ti: MQXC (CERN-CEA Collaboration)– Nb3Sn: HQ - MQXE (US LARP Collaboration)
• Larger aperture under consideration for Nb-Ti (MQXD) and Nb3Sn (MQXF)
• Preliminary design study of MQXF, a 140 mm aperture Nb3Sn quadrupole
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HQ
MQXC
Goals
• Investigate magnet parameters of an HQ-type quad. with the HQ cable and 140 mm aperture– How much do we lose in gradient?– How much do we increase the stress?
• Analyse the potential benefits of using a wider cable than HQ
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Outline
• From HQ to MQXF
• Magnet parameters
• Stress analysis
• Conclusions
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HQ
• Shell-based support structure– Pre-loaded with bladders– OD 570 mm, 1 m long
• Design focused on pre-load and alignment
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• Five assemblies and tests at 4.4 K carried out
• Max. grad. achieved: 170 T/m– 11.7 T estimated peak field– 86% of Iss at 4.4 K
From HQ to MQXFMagnetic design concept
• Two cases considered: 15 and 17 mm wide cable• 2 layers with similar angles and 4 blocks• All harmonics below 1 unit at 2/3 of Rin and 80% Iss
• Similar iron geometry with OD = 520 mm
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HQ MQXF_17mmMQXF_15mm
From HQ to MQXFMechanical design concept
• Same support structure concept as HQ• Same shell OD and thickness • Larger coil OD (aperture + thickness)• Collar-pad-yoke thickness reduced by 10 to 15 mm
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HQ MQXF_15mm MQXF_17mm
Outline
• From HQ to MQXF
• Magnet parameters
• Stress analysis
• Conclusions
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Strand properties
• 0.8 mm strand, 108/127• 53% Cu -> Cu/Su: 1.13
• Extr. strand meas. (HQ coil 3-4)– Jc (4.2 K, 12 T) of 3070 A/mm2 with
self field correction– This is considered a upper bound
for a production
• We assumed a Jc of 2800 A/mm2 with self field correction– This gives 2% reduction in gradient
(3 T/m) w.r.t. 3070 A/mm2
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Cable and coil parameters
• From HQ to MQXF_15mm– 11% more conductor
• From MQXF_15mm to 17mm– 16% more conductor
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Units HQ MQXF_15 mm MQXF_17 mm
Strand # 35 35 40
Thickness in/out mm 1.338/1.536 1.338/1.536 1.338/1.536
Width mm 15.150 15.150 17.314
Insulation thickness mm 0.100 0.100 0.100
Turns per oct. 46 51 52
Area supercond. per oct. mm2 380 422 491
MQXF_15mm MQXF_17mm
Magnet parameters at 1.9 K
• From HQ to MQXF_15mm– Loss of 14% in gradient– 25% increase of stored energy
• 15mm or 17mm ?– Increase of gradient +3% with
16% more conductor and 15% more stored energy
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Units HQ MQXF_15 mm MQXF_17 mm
Temperature K 1.9 1.9 1.9
Loadline margin % 20 20 20
Gradient T/m 169 145 149
Peak field T 11.7 11.9 12.1
Stored energy MJ/m 0.85 1.06 1.22
MQXF_15mm MQXF_17mm
Fringe field at 500 mm from the center
• W.r.t. Nb-Ti version, smaller yoke OD (520 mm) – Thicker shell (25 mm), and still missing the LHe vessel (5-10 mm thick)
• From HQ to MQXF_15mm– Fringe field from 0.68 to 9.77 T
• From MQXF_15mm to 17mm– Fringe field increases to 18.55 T
• Is it tolerable ? Is shielding necessary ? Further studies needed
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80% Iss
HQ MQXF_15mm MQXF_17mm
Outline
• From HQ to MQXF
• Magnet parameters
• Stress analysis
• Conclusions
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Stress analysisThe HQ case at 169 T/m (80% of Iss)
• 2D comp. stress– Increase pre-load
during cool-down– Pole turn always under
pressure
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Stress analysisThe HQ01e case: pole gauges measurements
• Pole azimuthal stress vs. I2 during training quench up to 170 T/m
• Linear variation up to maximum current
• No signs of unloading and pole-coil detachment
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Stress analysisThe HQ case at 169 T/m (80% of Iss)
• Coil peak stress located in inner layer – Pole turn during bladder-key operation– Pole turn after cool-down– Mid-plane turn during excitation
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Stress analysisComparison at 80% of Iss
• From HQ to MQXF_15mm– IL Lorentz stress: +13%– Peak stress: +15 MPa
• From MQXF_15mm to 17mm– Reduction of 10 MPa in peak
stress
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Units HQ MQXF_15 mm MQXF_17 mm
IL OL IL OL IL OL
Lorentz stress MPa -100 -120 -113 -128 -108 -128
Axial forces and support• From HQ to MQXF_15mm
– Increase of axial force: 25%• From MQXF_15mm to 17mm
– Increase of axial force : 15%
• Axial support– Stainless steel end plate (50 mm thick)– Aluminum axial rods (34 mm diameter)
• Maximum rod stress in MQXF– 350 (80% of Iss) to 500 MPa (100% of Iss)
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Units HQ MQXF_15 mm MQXF_17 mm
80% Iss 100% Iss 80% Iss 100% Iss 80% Iss 100% Iss
Axial force MN 0.85 1.32 1.06 1.63 1.22 1.87
Conclusions• A preliminary design of the 140 mm bore Nb3Sn quadrupole magnet MQXF
based on the HQ design has been carried out
• From HQ to MQXF (in operational cond.)– Gradient: from 169 to 145 T/m– Stored energy: from 0.85 to 1.06 MJ/m– Fringe field: from 0.68 to 9.77 mT – Peak stress: from 140 to 150 MPa
• According to a preliminary 2D mech. analysis, the HQ structure is capable provide pre-load to a 140 mm aperture coil up to Iss
• Increasing the cable by 2 mm provides additional 4 T/m with a reduction of 10 MPa in coil peak stress, but 15% more conductor and stored energy
• Next step– Further optimization of cable, coil, and support structure
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Appendix
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Stress analysisComparison at 100% of Iss
• Similar conclusions as at 80% of Iss
• Support structure– Bladder pressure
• Up to 55 MPa– Shell max stress
• Up to 340 MPa at 4.5 K– Iron maximum tension
• Below 200 MPa
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Units HQ MQXF_15 mm MQXF_17 mm
IL OL IL OL IL OL
Lorentz stress MPa -154 -184 -173 -193 -167 -195
HQ parameters
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MQXF_15mm parameters
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MQXF_17mm parameters
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Stress analysisCoil stress in TQ & HQ with e.m. forces at 1.9 K Iss
• Technology quadrupole TQ– 90 mm bore, 10 mm cable– Outer layer overcompressed
by -60 MPa at max. gradient
• High field quadrupole HQ– 120 mm bore, 15 mm cable– Inner and outer layer with
low stress at max gradient
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0 MPa
-60 MPa
0 MPa
0 MPa
Stress analysisThe HQ case at 169 T/m (80% of Iss)
• Contact pressure (positive) coil-pole at 4.4 K
• Contact pressure (positive) coil-pole with e.m. forces
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Saturation effect to Iss
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Support structure options
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